A comprehensive review on micro-plastic pollution in African aquatic systems

The distribution of micro-plastics (MPs) has been documented all over the world though there is a paucity of data in Africa. The study aimed to recapitulate existing information on MP pollution in African aquatic environments and to identify existing research gaps. Only 42% of the studies reported on polymer type citing lack of availability of Fourier Transform Infrared Spectroscopy or other instrumental equipment. Nonetheless, the polymer types descended in the order of polystyrene > polypropylene > polyester and the shapes ascended in sequence of films < fibres < fragments. An evident impediment on MP pollution research in African is variations in study methodology which restricts inter-study comparisons. Only 39% of the reviewed publications on MP pollution in Africa reported on freshwaters with the largest portion in the southern hemisphere. Wastewater treatment plant effluent discharge into waterways and dense urban population densities around riparian systems are major driving factors of MP pollution in African aquatic environments. The situation is further aggravated by mismanagement of plastic wastes along with poor maintained wastewater infrastructures. Units for reporting MP abundance needs to be standardized on the continent and it is suggested that units for measurement of MPs should be reported as particles•g−1 or particles•m−2 for sediments, particles•dm−3 or particles•L−1 in water and particles•individual−1 in fauna. In future, MP pollution research on the continent ought to investigate the interaction of MP with toxic pollutants along with spatiotemporal distribution of MPs in freshwater systems. Scholars across the continent need to shift from examining one environmental media but to rather have a holistic approach and seek to investigate all three matrices (i.e. water, sediments & fauna).